Historic and Spatial Variation of Lake Whitefish Maturation Schedules

Grant: # 0662

Grant Amount: $107,290.13

Board Decision Year: 2005

University of Michigan - Cooperative Institute for Limnology and Ecosystem Research (Ann Arbor)

Cooperative Institute for Limnology and Ecosystem Research

Hook, Tomas ([email protected]) (734) 741-2388

GLFT - Ecosystem Health and Sustainable Fish Populations-D - Ecological and biological fisheries research to inform management

Project Details

This project involved exploration of spatial and temporal variation in maturation

schedules of Great Lakes lake whitefish (Coregonus clupeaformis). The purpose of the

project was essentially two-fold. First, to analyze extant data on lake whitefish

maturations schedules in lakes Michigan, Huron and Superior. Second, to use ecogenetic individual based models to explore how ecological processes and anthropogenic

activities (e.g., size-selective fisheries harvest) may shape genetically determined

maturation schedules and growth rates.

We analyzed maturation data collected by the Chippewa-Ottawa Resource Authority

(Michigan, Huron and Superior), Ontario Ministry of Natural Resources (Huron) and

Michigan Department of Natural Resources (Michigan and Superior). We estimated ages

and lengths at 50% maturity, age-specific maturation ogives (age-specific probability of

being mature), and midpoints of probabilistic maturation reaction norms (PMRN; a

metric that accounts for plastic effects of growth and mortality). These different

maturation indices varied significantly among sexes and systems. Notably, midpoints of

lake-sex-age-specific estimates of PMRN were smallest for Lake Michigan fish,

intermediate for fish in the main basin of Lake Huron, and largest for fish in Lake

Huron’s Georgian Bay and Lake Superior. These spatial patterns in PMRN suggest that

there is intrinsic variation in maturation schedules of lake whitefish from different

regions of the Great Lakes. Recently, with the invasion of dreissend mussels and the

collapse of Diporeia (an historically important prey for lake whitefish) the age at 50%

maturity in lakes Huron and Michigan has increased. However, age-specific PMRNs

have not expressed similar temporal trends, suggesting that shifts in age at 50% maturity

are primarily plastic responses to limited food resources.

We developed and applied multi-generational eco-genetic models to consider how

ecological processes and anthropogenic-induced selection pressures (e.g., size-selective

fishing) may influence phenotypically plastic life history traits; growth and maturation

schedules (i.e., traits whose expression are determined by both genetic factors and

ecological interactions). We initially focused on a complex, detailed model of lake

whitefish. However, the application and interpretation of such a complex model was not

straightforward. Thus, we also developed a less complex, generalized model. Our

models are demonstrative of the potential influence of both anthropogenic and ecological

factors (mortality rate, density-dependent growth) and the interactive effects of growth

and maturation on the inheritance of these two life-history traits.

Documents

Final Report

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